The present invention relates to a method and a system for controlling the idle rotational speed of an internal combustion engine.
In the case of trouble in the operation of an idle rotational speed control system in which a solenoid valve is left open or a power transistor is left on, a conventional method of preventing an increased idle speed is by controlling the exhaust gas reflux (hereinafter referred to as the EGR) valve in such a manner as to open this valve, as disclosed in JP-A-57-186038. The disadvantage of this method, however, is that a change in the amount of EGR deteriorates the combustion and renders the engine speed unstable.